Fact check: Scott Pruitt on climate change, again

Scott Pruitt, President Donald Trump's controversial appointment to head the EPA, spelled out his vision for the agency at a key gathering of conservatives outside Washington, D.C. on Saturday. (Feb. 25)
AP

The head of the Environmental Protection Agency told CNBC that he “would not agree” that “human activity,” or carbon dioxide emissions, is the “primary contributor” to global warming. But climate scientists say it’s “extremely likely” that human activity, including CO2 emissions, is the main cause of warming since the mid-20th century.

Kernen, March 9: "Do you believe that it’s been proven that CO2 is the primary control knob for climate? Do you believe that?"

Pruitt: "No I, no I think that, that measuring with precision human activity on the climate is something very challenging to do and there’s tremendous disagreement about the degree of impact. So no, I would not agree that it’s a primary contributor to the, to the global warming that we see. But we don’t know that yet, as far as, we, we need, we need to continue the debate, continue the review and the analysis."

As we have written, Pruitt and others in President Trump’s Cabinet have taken the position lately that the climate is changing and humans have contributed, but they have said that scientists can’t measure or don’t understand human impact precisely. As we’ve said, scientists can measure that impact with varying levels of certainty and precision.

This time Pruitt went a little further when he disagreed that “human activity,” or CO2 emissions, is a “primary contributor.” We asked the EPA whether Pruitt was referring to human activity generally or just CO2 emissions, but EPA spokeswoman Julia Valentine declined to answer our question. So we’ll address both human activity’s contribution as a whole and CO2 emissions in particular.

According to the U.N.’s Intergovernmental Panel on Climate Change’s fifth assessment report, it is “extremely likely” (at least 95% probable) that more than half of the observed temperature increase since the mid-20th century is due to human, or anthropogenic, activities.

IPCC, 2014: "Anthropogenic greenhouse gas emissions have increased since the pre-industrial era, driven largely by economic and population growth, and are now higher than ever. This has led to atmospheric concentrations of carbon dioxide, methane and nitrous oxide that are unprecedented in at least the last 800,000 years. Their effects, together with those of other anthropogenic drivers, have been detected throughout the climate system and are extremely likely to have been the dominant cause of the observed warming since the mid-20th century."

To be clear, increased anthropogenic greenhouse gas emissions aren’t just caused by the burning of fossil fuels, and they don’t just include CO2. Other greenhouse gases include methane and nitrous oxide, and other sources include deforestation, decomposition of wastes in landfills and agriculture. Still, the report adds, “Emissions of CO2 from fossil fuel combustion and industrial processes contributed about 78% of the total GHG emissions increase from 1970 to 2010.”

What about natural contributors to global warming?

NASA explains that “carbon dioxide is released through natural processes such as respiration and volcano eruptions,” for example. The agency also says, “It’s reasonable to assume that changes in the sun’s energy output would cause the climate to change, since the sun is the fundamental source of energy that drives our climate system,” adding that “studies show that solar variability has played a role in past climate changes.”

But when scientists who contributed to the IPCC report examined trends in global warming, they ruled out these natural factors as the primary cause. In fact, they are “virtually certain” (at least 99% probable) that natural climatic variability “alone cannot account for the observed global warming since 1951.”

FactCheck.org's SciCheck is made possible by a grant from the Stanton Foundation.

Environmental Protection Agency chief Scott Pruitt (L) is seen after France's President Emmanuel Macron addressed a joint meeting of Congress inside the House chamber on April 25, 2018, at the US Capitol in Washington, DC. MANDEL NGAN/AFP/GETTY IMAGES

A sign criticizing Environmental Protection Agency Administrator Scott Pruitt is seen posted on the base of a utility pole on the corner of H Street NW and 13 Street NW in Washington, Friday, April 6, 2018. Pruitt is currently embroiled in controversy related to an apartment he rented from a Capitol Hill lobbyist for $50 a night, personnel issues at the EPA, and accusations of wasting taxpayer money. CAROLYN KASTER/AP

Light is projected by the League of Conservation Voters as part of the new Boot Pruitt campaign onto the Ronald Reagan Building and International Trade Center, the location of the Environmental Protection Agency, March 28, 2018, in Washington. The images describe EPA Administrator Scott Pruitt's wasteful spending on luxury travel, ongoing investigations while in office, and dangerous policies that have imperiled public health. ALEX BRANDON/AP

Environmental Protection Agency Administrator Scott Pruitt testifies before the Senate Environment Committee on Capitol Hill in Washington on Jan. 30, 2018. Pruitt is once again understating the threat posed by climate change, this time by suggesting that global warming may be a good thing for humanity. Pruitt has been champion for the continued burning of fossil fuels while expressing doubt about the consensus of climate scientists that man-made carbon emissions are overwhelmingly the cause of record temperature increases observed around the world. In an interview with KSNV-TV in Las Vegas on Feb. 7, Pruitt made several statements that are undercut by the work of climate scientists, including those at his own agency. PABLO MARTINEZ MONSIVAIS/AP

In this April 19, 2017, file photo, Environmental Protection Agency Administrator Scott Pruitt speaks at a news conference with Pasquale "Nino" Perrotta, second from left, in East Chicago, Ind. Perrotta, the security chief for the head of the Environmental Protection Agency worked on the side as a private investigator for the owner of a tabloid news company with close ties to President Donald Trump. TERESA CRAWFORD/AP

EPA Administrator Scott Pruitt does a television interview in Statuary Hall at the U.S. Capitol before President Trump delivers a speech to a joint session of Congress on Feb. 28, 2017. Mark Wilson, Getty Images

Supreme Court Justice Samuel Alito shakes hands with Pruitt after swearing him in as the Environmental Protection Agency administrator in the Eisenhower Executive Office Building on Feb. 17, 2017. Holding the Bible is Marlyn Pruitt, wife of Scott Pruitt, and their son Cade Pruitt is standing second from right. Carolyn Kaster, AP

Pruitt is welcomed on Capitol Hill on Jan. 18, 2017, by Senate Environment and Public Works Chairman John Barrasso, R-Wyo., prior to testifying at his confirmation hearing before the committee. J. Scott Applewhite, AP